This invention relates to a continuous high speed process for texturing of thermoplastic synthetic fiber, especially texturing multifilament yarn to exceptionally high crimp levels. A particular feature of this invention is that the yarn is dimensionally stabilized or "set" by heat, in advance of the crimping operation, to low levels of shrinkage. Another feature is that the texturing is fast enough to allow coupling with a high-speed yarn drawing operation in a continuous process.
It is broadly known to couple the drawing and texturing of multifilament thermoplastic synthetic yarns, in particular polyethylene terephthalate ("PET") yarns which have been partially oriented to a birefringent value of about 15-30% of that observed in the drawn yarn, and having appreciable but low crystallinity as indicated by density. See Textile Research Journal, Feb. 1975, pp. 112-117, article by O. L. Shealy and R. E. Kitson.
A particular method of texturing thermoplastic synthetic yarn at high speed is taught in the U.S. patent application of Li, Oswald and Liland, Ser. No. 675,353, filed Apr. 9, 1976, now U.S. Pat. No. 4,074,405, granted 2/21/78 for "Method and Apparatus For Texturing Yarn" and in U.S. Pat. Nos. 4,024,610 and 4,024,611, both of May 24, 1977 to the same Li, Liland and Oswald.
Such method involves advancing and plasticizing a drawn synthetic yarn such as PET yarn drawn over a hot plate between two pairs of heated godets. The yarn is aspirated through a tube, sometimes called an "energy tube" in this art, with hot compressible fluid such as superheated steam; then the yarn strikes with sharp impact, as it issues from the energy tube, at an oblique angle against an unyielding barrier such as a moving perforate (including mesh) surface (especially a wire screen) within a chamber having a stationary cover and an outlet in the cover. A plug of the yarn in the chamber results from allowing a major portion of the fluid to pass out practically immediately, as through the perforate moving surface, and from the relatively slow advancement of the yarn as it is conveyed to the outlet from the chamber on such moving surface, moving at lower linear velocity than that of the yarn issuing from the energy tube. If desired, the yarn can be preheated before entering the energy tube; and/or a further amount of hot fluid can be introduced into the chamber for purposes of setting the crimps.
Another texturing method also involves forwarding incoming yarn by use of hot fluid such as superheated steam, into a chamber with provision for release of steam but without provision for an initial sharp impact of the yarn with an unyielding barrier. Thus, in U.S. Pat. No. 3,438,101 of Apr. 15, 1969 to Le Noir et al. for "Process and Apparatus for Texturizing Yarn," steam forces yarn through a tube onto a revolving wire screen forming the bottom of a peripheral chamber around a revolving drum, which chamber is covered over by an endless belt which drives the drum. The yarn is crimped by impingement against yarn compacted in the revolving chamber. Also, U.S. Pat. No. 4,019,228 of Apr. 26, 1977 to Ozawa et al. teaches use of an ejection nozzle whereby superheated steam forces yarn at high speed into a rotating stuffing chamber, covered with a stationary cover and having a peripheral screen surface. This apparatus is said to allow coupling known drawing processes with the crimping apparatus of the invention (Col. 7, lines 27-43; FIG. 10; FIG. 11; Examples 3, 4 and 6-9). The patent teaches also use of a yarn preheater upstream of the nozzle, operating to enhance the heat setting of the crimps formed by use of the apparatus (Col. 7, lines 16-26, FIG. 9 and Example 2).
Also of interest is U.S. Pat. No. 3,739,056 of June 12, 1973 to E. F. Evans et al. for "Draw/Relax/Anneal Process for Polyesters." This patent teaches processing of undrawn, amorphous polyester (such as PET) fibers including steps of drawing in a spray of heated liquid, relaxing in a steam jet, annealing at constant length by passing over a series of heated rolls, passing through a cooling spray, and passing to a "crimper 58" (Col. 2, lines 8-28 and FIG. 1). An alternative to annealing rolls is a hot plate (Col. 2, lines 38-52 and FIG. 3). The purpose of the relaxing and annealing is to develop both good tenacity and good dyeability (Col. 2, line 53-Col. 3, line 28).
Also to be noted is U.S. Pat. No. 3,665,567 of May 30, 1972 to Clarkson for "Yarn Rebound Texturing Apparatus and Method." Yarn carried by steam through a tube, is crimped by being hurled out of the tube longitudinally against a foraminous surface, from which it rebounds and then drops into a heat-setting chamber. The yarn prior to passage through the tube, is drawn in a conventional manner between two pairs of heated godet rolls.